Wafer product and processing method therefor

Abstract

A semiconductor wafer has two faces, one of which is a laser light incident face. A dicing sheet is attached to the other face of the wafer, so that it is stretched to thereby apply tensile stress to a laser-reformed region and cause cutting with the reformed region taken as a starting point for cutting. A protection layer, such as light scattering projections and depressions, a light scattering member or a light reflecting member, is provided between the wafer and the dicing sheet to scatter or reflect the laser light passing through the wafer. Thus, the dicing sheet can be protected from being damaged because the laser light converging point is not formed in the dicing sheet.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is based on and incorporates herein by reference Japanese Patent Applications No. 2005-331209 filed on Nov. 16, 2005, No. 2005-331218 filed on Nov. 16, 2005 and No. 2006-196890 filed on Jul. 19, 2006. FIELD OF THE INVENTION [0002] The present invention relates to a wafer product and a processing method for the wafer product. In particular, the present invention relates to a wafer product that is cut and separated by cutting with a reformed region due to multiphoton absorption, formed by irradiation with laser light, taken as a starting point for cutting and a processing method for the wafer product. BACKGROUND OF THE INVENTION [0003] Laser dicing technologies have been developed for cutting and separating (dividing) a wafer-like object to be processed into a plurality of chips using laser light. [0004] For example, a wafer-like object such as a semiconductor substrate to be processed is irradiated with laser light with a...

AI Technical Summary

Benefits of technology

[0022] According to the present invention, a wafer product separable by cutting at a reformed region formed by laser light comprises a wafer, a dicing sheet and a protection layer. The wafer has two faces, one of which is a laser light incident face and the other of which is opposite the light incident face in a direction of wafer thickness. The dicing sheet is attached to the other face of the wafer for cutting the wafer into a plurality of chips. The protection layer is provided between the wafer and the dicing sheet for scattering or reflecting the laser light passing though the wafer thereat to protect the dicing sheet from the laser light.

Problems solved by technology

However, in this technology, the light-converging point cannot be positioned inside the wafer in the cases, where there is variation from wafer to wafer and the wafer to be processed is too thin, or where the setting of the light-converging point of laser light is inappropriate.

That is, the focal point of laser light cannot be positioned inside the wafer when the wafer is too thin or when the setting of the focal point is inappropriate.

According to US 2005 / 0202596, for example, an expansible sheet attached to the rear face of a wafer can be melted and damaged due to laser light when the light-converging point of the laser light is positioned inside the sheet.

Thus, when the sheet is stretched to cut and separate the wafer, the tensile stress from the sheet cannot be evenly applied to the wafer.

Therefore, it becomes difficult to appropriately cut and separate the wafer.

In cases where the light-converging point of laser light is positioned within the stage (specimen support) of a laser machine with a wafer placed on it, the stage can be melted and damaged by the laser light and lose planarity.

Thus, when the next wafer is placed on the stage and irradiated with laser light, the light-converging point cannot be positioned in a desired position inside the wafer, and a reformed region cannot be formed in a due position.

As a result, it becomes difficult to accurately cut and separate the wafer with the reformed region taken as the starting point.

Because of this multiphoton absorption, a phenomenon designated as optical damage occurs at the light-converging point P and in the vicinity of the point within the wafer W. This induces thermal distortion and cracks to occur in that area.

As a result, great force is required to divide the substrate.

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